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https://www.readbyqxmd.com/read/29144560/large-proton-affinity-enhancements-triggered-by-non-covalent-interactions
#1
Carlos Martín-Fernández, M Merced Montero-Campillo, Ibon Alkorta, Manuel Yáñez, Otilia Mó, José Elguero
The proton affinity of the hydroxyl group of a series of compounds YHxOH (x=0-3, Y = Li, Na, Be, Mg, B, Al, Si, P, S, Cl, H) always increases upon interaction with Lewis bases LB = NH3, H2CNH, HCN, according to electronic structure calculations carried out at the G4 level of theory. The LB:YHxOH complexes experiment proton affinity enhancements from 24.8 to 304.8 kJ·mol-1 on its OH group with respect to the free compounds. This enhancement is related to the ability of these YHxOH compounds, acting as Lewis acids, to form non-covalent interactions of different kinds...
November 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29144135/parameterization-of-palmitoylated-cysteine-farnesylated-cysteine-geranylgeranylated-cysteine-and-myristoylated-glycine-for-the-martini-force-field
#2
Yoav Atsmon-Raz, D Peter Tieleman
Peripheral membrane proteins go through various post-translational modifications that covalently bind fatty acid tails to specific amino acids. These post translational modifications significantly alter the lipophilicity of the modified proteins and allow them to anchor to biological membranes. Over 1000 different proteins have been identified to date that require such membrane-protein interactions in order to carry out their biological functions, including members of the Src and Ras superfamilies that play key roles in cell signaling and carcinogenesis...
November 16, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29144130/structural-phase-transitions-in-ptin2-at-high-pressure-a-theoretical-investigation
#3
P Modak, Ashok K Verma
A study of the bonding and electronic properties of intermetallics under pressure is crucial in the design and development of novel materials for useful applications. These properties are largely controlled by the underlying crystal structures. Here we investigated the high-pressure structural behavior of PtIn2 using crystal structure search calculations, which efficiently combine evolutionary algorithms and state-of-the-art density functional theory. Three new crystal structures, namely, Fe2B-type (I4/mcm, Z = 2), cotunnite-type (Pnma, Z = 4), and monoclinic (C2/m, Z = 2), are proposed at about 9...
November 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29143988/synthesis-and-optical-properties-of-phenanthroline-derived-schiff-base-like-dinuclear-ru-ii-ni-ii-complexes
#4
Hannah Kurz, Charles Lochenie, Kristina G Wagner, Sandra Schneider, Matthias Karg, Birgit Weber
Two phenanthroline-derived Schiff base-like ligands with a covalently-linked Ru(II) phosphorescent unit were synthesised and converted into bimetallic Ru(II)-Ni(II) complexes. The optical properties were studied to examine a possible photoluminescence quenching through a non-radiative energy transfer upon Coordination Induced Spin State Switch (CISSS) at the Ni(II) centre. Therefore the metalloligands and the Ni(II) complexes were studied by UV-Vis absorbance as well as steady-state and time-resolved emission spectroscopy in MeCN and pyridine solutions...
November 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29143785/waterborne-polyurethane-coatings-with-covalently-linked-black-dye-sudan-black-b
#5
Tao Wang, Wei Sun, Xingyuan Zhang, Haiyan Xu, Fei Xu
Colored waterborne polyurethanes have been widely used in paintings, leathers, textiles, and coatings. Here, a series of black waterborne polyurethanes (WPUs) with different ratios of black dye, Sudan Black B (SDB), were prepared by step-growth polymerization. WPU emulsions as obtained exhibit low particle sizes and remarkable storage stability at the same time. At different dye loadings, essential structural, statistical and thermal properties are characterized. FTIR (fourier transform infrared) spectra indicate that SDB is covalently linked into waterborne polyurethane chains...
October 28, 2017: Materials
https://www.readbyqxmd.com/read/29143041/joint-experimental-and-theoretical-studies-of-the-surprising-stability-of-the-aryl-pentazole-upon-noncovalent-binding-to-%C3%AE-cyclodextrin
#6
Yu-Zhang Yang, Xiao-Feng Liu, Ru-Bo Zhang, Si-Ping Pang
Herein, binding of the β-cyclodextrin (β-CD) host to the unstable aryl pentazole guest has been confirmed experimentally and theoretically. After the confinement of aryl pentazole, electron density reorganization was studied by M06-2X dispersion-corrected DFT and further reflected in the characteristic shift in the NMR spectra. Among the host-guest complexes, the inclusion complex is favored with the phenyl ring expectedly encapsulated within the cavity through noncovalent interactions such as hydrogen bonding, C-Hπ, and the special Csp(2)-HH-Csp(3) bonding discovered by the NBO, QTAIM, and NCI-RDG theories...
November 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29143030/quantitative-chemoproteomic-profiling-reveals-multiple-target-interactions-of-spongiolactone-derivatives-in-leukemia-cells
#7
M H Wright, Y Tao, J Drechsel, J Krysiak, S Chamni, A Weigert-Munoz, N L Harvey, D Romo, S A Sieber
The spongiolactones are marine natural products with an unusual rearranged spongiane skeleton and a fused β-lactone ring. These compounds have potential anticancer properties but their mode of action has yet to be explored. Here we employ activity-based protein profiling to identify the targets of a more potent spongiolactone derivative in live cancer cells, and compare these to the targets of a simpler β-lactone. These hits provide the first insights into the covalent mechanism of action of this natural product class...
November 16, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29143027/surface-confined-2-2-cycloaddition-towards-one-dimensional-polymers-featuring-cyclobutadiene-units
#8
Bay V Tran, Tuan Anh Pham, Michael Grunst, Milan Kivala, Meike Stöhr
Surface-confined synthesis has been offering a wide range of opportunities for the construction of novel molecular nanostructures. Exploring new types of on-surface coupling reactions is considered essential for being able to deliberately tune the materials properties. Here, we report on the formation of a covalent C-C bonding motif, namely 1,3-cyclobutadiene, via surface-confined [2 + 2] cycloaddition between pyrene moieties using low temperature scanning tunneling microscopy (LT-STM) and X-ray photoemission spectroscopy (XPS) measurements...
November 16, 2017: Nanoscale
https://www.readbyqxmd.com/read/29142998/covalent-post-assembly-modification-in-metallosupramolecular-chemistry
#9
REVIEW
Derrick A Roberts, Ben S Pilgrim, Jonathan R Nitschke
A growing variety of covalent reactions have been employed to achieve the post-assembly modification (PAM) of self-assembled metallosupramolecular complexes. Covalent PAM enables the late-stage derivatisation of pre-assembled parent complexes in a modular fashion, thus expanding the chemical space available for supramolecular synthesis. The oldest and most widespread implementation of covalent PAM is in metal-preorganised covalent synthesis. Recent work, however, has broadened the scope of covalent PAM to include: protocols for efficiently grafting new functionalities onto supramolecular architectures, reactions that permanently 'lock-down' metastable complexes, and covalent bond-forming stimuli that trigger controlled structural transformations between distinct supramolecular species...
November 16, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/29141539/comparative-selectively-targeted-anti-neoplastic-cytotoxicity-of-three-immunopharmaceuticals-with-covalently-bound-fludarabine-gemcitabine-and-dexamethasone-moieties-synthesized-utilizing-organic-chemistry-reactions-in-a-multi-phase-regimen
#10
Cody P Coyne, Lakshmi Narayanan
Background - Unintentional passive diffusion of conventional small molecular weight pharmaceuticals across intact membranes of normal healthy cells in tissues and organ systems induces sequelae that limit therapeutic dosage and duration of administration. Selective "targeted" delivery of pharmaceuticals is a molecular strategy that can potentially provide heightened margins-of-safety with greater potency and improved efficacy. Materials-and-Methods - Monophosphate analogs of fludarabine, gemcitabine, and dexamethasone were combined with a carbodiimide reagent in the presence of imidazole to produce reactive intermediates that were subsequently covalently bound to monoclonal anti-IGF-1R or anti-EGFR IgG-immunoglobulin...
November 14, 2017: Current Pharmaceutical Design
https://www.readbyqxmd.com/read/29141403/lipogels-for-encapsulation-of-hydrophilic-proteins-and-hydrophobic-small-molecules
#11
Celia C Homyak, Ann Fernandez, Mollie A Touve, Bo Zhao, Francesca Anson, Jeanne A Hardy, Richard W Vachet, Nathan C Gianneschi, Jennifer L Ross, S Thayumanavan
Lipid-polymer hybrid materials have the potential to exhibit enhanced stability and loading capabilities in comparison to parent liposome or polymer materials. However, complexities lie in formulating and characterizing such complex nanomaterials. Here we describe a lipid-coated polymer gel (lipogel) formulated using a one-pot methodology, where self-assembling liposomes template a UV-curable polymer gel core. Using fluorescently-labeled lipids, protein, and hydrophobic molecules, we have characterized their formation, purification, stability, and encapsulation efficiency via common instrumentation methods such as dynamic light scattering (DLS), matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS), UV-Visible spectroscopy, fluorescence spectroscopy, and single particle total internal reflection fluorescence (TIRF) microscopy...
November 15, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/29141116/fluorine-in-a-c-f-bond-as-the-key-to-cage-formation
#12
Maxwell Gargiulo Holl, Cody Ross Pitts, Thomas Lectka
Cage molecules have long been employed to trap reactive or fleeting species, as their rigid nature allows them to enforce situations that otherwise would not persist. In this minireview, we discuss our use of rigid cage structures to investigate the close noncovalent interactions of fluorine with other functional groups and determine how mutual proximity affects both physical properties and reactivity. Unusual covalent interactions of fluorine are also explored: the cage can close to form the first solution-phase C-F-C fluoronium ion...
November 15, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29140700/high-pressure-behavior-of-silver-fluorides-up-to-40-gpa
#13
Adam Grzelak, Jakub Gawraczyński, Tomasz Jaroń, Dominik Kurzydłowski, Armand Budzianowski, Zoran Mazej, Piotr J Leszczyński, Vitali B Prakapenka, Mariana Derzsi, Viktor V Struzhkin, Wojciech Grochala
A combined experimental-theoretical study of silver(I) and silver(II) fluorides under high pressure is reported. For Ag(I), the CsCl-type structure is stable to at least 39 GPa; the overtone of the IR-active mode is seen in the Raman spectrum. Its Ag(II)F2 sibling is a unique compound in many ways: it is more covalent than other known difluorides, crystallizes in a layered structure, and is enormously reactive. Using X-ray diffraction and guided by theoretical calculations (density functional theory), we have been able to elucidate crystal structures of high-pressure polymorphs of AgF2...
November 15, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29140680/helicity-inversion-of-supramolecular-hydrogels-induced-by-achiral-substituents
#14
Guofeng Liu, Xin Li, Jianhui Sheng, Pei-Zhou Li, Wee Kong Ong, Soo Zeng Fiona Phua, Hans Ågren, Liangliang Zhu, Yanli Zhao
Probing the supramolecular chirality of assemblies and controlling their handedness are closely related to the origin of chirality at supramolecular level and the development of smart materials with desired handedness. However, it remains unclear how achiral residues covalently bonded to chiral amino acids can function in the chirality inversion of supramolecular assemblies. Herein, we report macroscopic chirality and dynamic manipulation of chiroptical activity of hydrogels self-assembled from phenylalanine derivatives, together with the inversion of their handedness achieved solely by exchanging achiral substituents between oligo(ethylene glycol) and carboxylic acid groups...
November 15, 2017: ACS Nano
https://www.readbyqxmd.com/read/29140075/strictosidine-synthase-triggered-enantioselective-synthesis-of-n-substituted-s-3-14-18-19-tetrahydroangustines-as-novel-topoisomerase-i-inhibitors
#15
Yunrui Cai, Huajian Zhu, Zaccary Alperstein, Wenjun Yu, Artem Cherkasov, Hongbin Zou
Monoterpenoid indole alkaloids (MIAs) comprise an important class of molecules for drug discovery, and these have variant carbon skeletons with prominent bioactivities. For instance, in spite of limitations to their use, camptothecins are the only clinically approved Topoisomerase I (Top1) inhibitors. The enzyme STR1, which is key for MIA biosynthesis, was applied to the enantioselective preparation of three N-substituted (S)-3,14,18,19-tetrahydroangustine (THA) derivatives. These non-camptothecin MIAs were shown to have moderate in vitro HepG2 cytotoxicity and Top1 inhibition activities...
November 15, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/29139578/structure-property-relationships-in-cuii-binding-tetramolecular-g-quadruplex-dna
#16
David M Engelhard, Lukas M Stratmann, Guido H Clever
A series of artificial metal-base tetrads composed of a CuII cation coordinating to four pyridines, covalently attached to the ends of tetramolecular G-quadruplex DNA strands [LA-Dd(G4)]4 (LA-D = ligand derivatives), was systematically studied. Structurally, the square-planar [Cu(pyridine)4] complex behaves analogous to the canonical guanine quartet. Copper coordination to all studied ligand derivatives was found to increase G-quadruplex thermodynamic stability, tolerating a great variety of ligand linker lengths (1 - 5 atoms) and thus demonstrating the robustness of the chosen ligand design...
November 15, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29139184/achieving-strong-positive-cooperativity-through-activating-weak-non-covalent-interactions
#17
Yan-Long Ma, Hua Ke, Arto Valkonen, Kari Rissanen, Wei Jiang
Positive cooperativity achieved through activating weak non-covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new naphthotubes have been synthesized and the syn isomer binds DABCO-based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion-pairing interactions. The X-ray single-crystal structure revealed that the strong positive cooperativity likely originates from eight C-H⋅⋅⋅O hydrogen bonds between the two head-to-head-arranged syn tube molecules...
November 14, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29138771/near-infrared-aza-bodipy-fluorescent-probe-for-selective-cu-2-detection-and-its-potential-in-living-cell-imaging
#18
Yordkhuan Tachapermpon, Sopida Thavornpradit, Adisri Charoenpanich, Jitnapa Sirirak, Kevin Burgess, Nantanit Wanichacheva
A near-infrared (NIR) fluorescent sensor 1 composed of an aza-boron-dipyrromethene (aza-BODIPY) core covalently bound to two di-2-picolylamine moieties was conceived for Cu(2+) detection in aqueous solutions. Spectroscopic properties and binding abilities with several metal ions were investigated in phosphate buffered saline (pH 7.4): acetonitrile (95 : 5 v/v) with Triton X-100 via fluorometric titrations. The fluorescence of sensor 1 was quenched selectively by cupric ions in the presence of alkali- and transition-metal-ions...
November 15, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29138441/screening-based-approach-and-dehydrogenation-kinetics-for-mgh2-guide-to-find-suitable-dopant-using-first-principles-approach
#19
E Mathan Kumar, A Rajkamal, Ranjit Thapa
First-principles based calculations are performed to investigate the dehydrogenation kinetics considering doping at various layers of MgH2 (110) surface. Doping at first and second layer of MgH2 (110) has a significant role in lowering the H2 desorption (from surface) barrier energy, whereas the doping at third layer has no impact on the barrier energy. Molecular dynamics calculations are also performed to check the bonding strength, clusterization, and system stability. We study in details about the influence of doping on dehydrogenation, considering the screening factors such as formation enthalpy, bulk modulus, and gravimetric density...
November 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29138295/generation-of-specific-inhibitors-of-sumo-1-and-sumo-2-3-mediated-protein-protein-interactions-using-affimer-adhiron-technology
#20
David J Hughes, Christian Tiede, Natalie Penswick, Anna Ah-San Tang, Chi H Trinh, Upasana Mandal, Katarzyna Z Zajac, Thembaninskosi Gaule, Gareth Howell, Thomas A Edwards, Jianxin Duan, Eric Feyfant, Michael J McPherson, Darren C Tomlinson, Adrian Whitehouse
Because protein-protein interactions underpin most biological processes, developing tools that target them to understand their function or to inform the development of therapeutics is an important task. SUMOylation is the posttranslational covalent attachment of proteins in the SUMO family (SUMO-1, SUMO-2, or SUMO-3), and it regulates numerous cellular pathways. SUMOylated proteins are recognized by proteins with SUMO-interaction motifs (SIMs) that facilitate noncovalent interactions with SUMO. We describe the use of the Affimer system of peptide display for the rapid isolation of synthetic binding proteins that inhibit SUMO-dependent protein-protein interactions mediated by SIMs both in vitro and in cells...
November 14, 2017: Science Signaling
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